Mirena pregnancy chance

My boyfriend wants to cum in me, I’m on the mirena iud but I still don’t want to deal with getting pregnant. I’ve told him it’s more likely to have an ectopic pregnancy on the mirena, and I definitely don’t want that.

We’ve taken the risk twice before but that was in the first year of having the mirena. I’ve had it 2 years and I know the effectiveness lowers a bit more each year.

Does anyone on the mirena iud track their periods for the purpose of knowing when you’re ovulating and not ovulating? Or anyone had a similar situation?